1. Field of the Invention
The invention relates to an apparatus for diminishing intake vortexes in jet engines with turbo-compressors of aircrafts during test runs.
2. Background Art
For routine check-outs of the jet engines of an aircraft, static test runs on the ground are necessary, in which the engines are loaded to their limit of capacity. To that end, aircraft manufacturers indicate upper limits for the wind velocity in dependence on the wind direction relative to the aircraft axis, which tapper limits have to be taken into account during the test runs. The necessity of these restrictions results from the fact that in case of unfavorable wind conditions, in the intake stream of the engine, very high disturbances of the field of velocity are created by extensive vortex structures, in particular by a concentrated, strong individual vortex spread from the ground, which vortex may cause malfunctions of the engine process with a possible shortening of engine life. Therefore, for the engine test, the aircraft is placed in the wind so that the engines are blown against as axially from the front as possible.
Often, the standing direction of the aircraft on the test location is predetermined, e.g. whenever there is a noise protection facility available which is stationary on the ground, as it is described for example in U.S. Pat. No. 4,958,700. When constructing such facilities, the prevailing wind direction at the site often cannot be taken into consideration, but an already existing built-up area is decisive for the intended noise protection. However, in this case the number of tests to be conducted under these prerequisites can be considerably restricted, as the cited vortex structures are more likely to be generated, and may develop a higher strength, due to an unfavorable blower stream or due to close walls or edges of the noise protection facility, respectively.
The air quantity taken in by the turbo-compressor of an engine depends on the type, while the air velocity in the intake stream locally may clearly be more than 100 m/s. In this intake stream, as a rule a concentrated vortex is generated with the taken in air masses rotating about the axis of the vortex. The vortex may originate from a near edge, a near wall or also from the ground. The axis of the vortex may be visualized from the place of origin as far as into the engine inlet. In this case this vortex is not stationary, but its starting point moves, its axis deforms and also the place of entrance into the engine changes. As a rule, shortly after its creation, the movement range of the concentrated vortex stabilizes to a limited region in front of the engine, the starting point of the vortex moving to and fro in the boundary layer of the ground in front of the engine inlet. At this time, the vortex reaches its highest strength. The strength of the vortex, however, is the decisive variable for malfunctions in the compressor of the engine in form of burbles and in the combustion chamber of the engine in form of critical conditions, which may result in an emergency shutdown of the engine.